Plural component road marking systems consist of a resin or resinous material as being one component and a catalyst, (reactor--hardener) being the other component. To complete the system a third component, the reflective agent, which may also be made up of one or more components, is added, usually as a secondary operation to the spraying of the resin and catalyst. The two components, i.e., the resin and the catalyst must be brought together in a given ratio to facilitate the curing, hardening, of the material once applied. It is crucial that the mix of the two components be thorough, complete and accurate. Failure to achieve a thorough and proper mix, will result in various application failures, ranging from partial to full failures. An uncured line will not adhere to the road surface, leaving the roadway unmarked. In the interim moving traffic will track the uncured material indiscriminately across the road surface. The material will also be splashed onto auto finishes and glass areas causing considerable and expensive damage to autos. Improper curing because of improper application will also result in various failures. In addition to the hazards presented by a failed line, the correction is expensive and time consuming.
Slower drying materials require the use of traffic barriers to prevent moving traffic from tracking through slowly curing lines. These barriers may be a follow vehicle with warnings to traffic behind the striper to not pass or come between the striper and follow vehicle and the placement of traffic cones beside the new line to warn traffic not to come into the line. These traffic inhibitors are dangerous to both the motorist and workers and are the cause of many accidents resulting in death and serious injuries.
Newer developments in materials over the last few years have presented additional problems in the application and use of multiple component marking systems. To reduce some of the previous mentioned problems, primarily associated with slower cure times, faster curing materials such as those disclosed in U.S. Pat. No. 5,478,596 Richard S. Gurney have been developed. Some of the materials developed and certainly those to be developed in the future, set so fast, that the standard static mixing tube applicator system will no longer work. For clarification, a static mixing tube system relies on the resin and catalyst being physically mixed together by forcing the two materials together as they are flowed through a common tube with intermittent flow restrictor inside the tube, thereby causing the materials to "twist" together. This system is archaic, and in fact insures that there will be at least parts of the application that will be improper. The two materials do not like each other and tend to resist mixing. In addition, this system requires frequent flushing with solvents to keep the system operational, (if not flushed, the mixed materials in the tube cake cure and block the tube). The solvents are not environmentally safe and by Federal and state laws are prohibited from being `dumped` on the ground. The solvents also degrade the road surface in the case of composite roads, by dissolving the tars holding the composite together, and causing the road to disintegrate. These solvents are poisonous and dangerous to humans and animals.
Many factors affect the final result, i.e., the materials meeting the road surface in the correct ratio and properly mixed to achieve cure as prescribed by the formula, slow enough to allow the injection of a reflective media prior to cure, fast enough to keep the reflective media from sinking to the bottom and being covered by the material; the definition of the line dimensionally and physically, being of proper width, thickness, uniformity, edge definition and square start and finish.
The considerations that must be given within a multi component spray system are factors governed by the characteristics of the material components. The component materials, rate of flow and the nature in which it flows as well as the various variables that enhance or inhibit the flow of the materials, including ambient heat, heat caused by flow, friction and resistance. Size of hose and pipe, valves, orifices, turns and radii all have an impact on the movement of the material components from a supply tank to the spray tip. The material components must arrive at the mix chamber and flow into the mix chamber in the exact ratio required to achieve the desired result. The two components do not have the same characteristics of flow at the same temperature and a line spray system operates in an environment that is unpredictable, that is outdoor weather has many variables that impact the temperature gain or loss of the material at various points in the system. A warm day with a high wind can cause heat loss that would be more severe than a cooler day with no wind.
It is imperative that when a line spray system is activated and material is sprayed from the gun, that all systems arc in synchronous harmony to assure a perfect line at each start. With archaic systems, the only way this could be accomplished was to actually place a bucket under the gun and activate the gun until the system was producing materials in the correct proportion to cure. This was wasteful, time consuming and only a viable solution for a start-up, with no assurance that for temporary delays, such as a long wait at an intersection, that the gun did not freeze-up, or have an improper mix.